1. Field of the Invention
The present invention relates to a magneto-optical disc apparatus in which data can be recorded on or played-back from a magneto-optical disc loaded therein.
2. Description of Related Art
For example, in a conventional magneto-optical disc apparatus in which data can be repeatedly recorded on a magneto-optical disc, intensive laser beams emitted from an optical head are continuously converged onto a recording layer of the magneto-optical disc to raise the temperature to the Curie temperature. At the Curie temperature, a magnetic field is applied by a biasing magnetic field generator (i.e., magnetic head) to make the direction of magnetization of a magnetic substance coincident with that at the initialization thereof. Thereafter, the biasing magnetic field is inverted, so that laser beams of high power can be discontinuously converged onto the recording layer to invert the direction of magnetization and thereby record data on the recording layer.
In this type of magneto-optical disc apparatus, upon rewriting data of each track of the magneto-optical disc, it is necessary to rotate the magneto-optical disc to erase and record data, resulting in a decreased recording speed. To solve this problem, a magnetic modulation overwriting type of magneto-optical disc apparatus has been proposed, in which the magnetic field of S or N is intermittently applied to a small area on which the laser beams are to be converged. In such an apparatus, one rotation of the magneto-optical disc enables data to be rewritten.
In a known magnetic modulation overwriting type of magneto-optical disc apparatus, it is necessary to apply a magnetic field which has been quickly modulated to the magneto-optical disc to thereby realize a quick overwriting. To this end, it is necessary to miniaturize the magnetic head which must be placed as close as possible to the recording layer of the magneto-optical disc. However, if placed too close, the magnetic head may accidentally come into contact with the glass (or resin) surface of the magneto-optical disc during rotation thereof. This will be particularly likely if the magnetic head becomes unstably loaded with respect to the magneto-optical disc. For the preceding reasons, it has become necessary to realize a simple magneto-optical disc apparatus in which a magnetic head is stably held as close as possible to a photo magnetic disc, at a loaded position thereof, without accidentally coming into contact with the magneto-optical disc.